Aerial photography is almost as old as photography itself. As soon as people were able to rise above the earth using man made conveyances, the usefulness of imaging various features on the ground was immediately evident. Aerial photography using color photographic films is more recent, but still decades old. The particular characteristics required for such films are high contrast, low minimum density (D.sub.min) and high resolution (ability to reproduce fine detail) and sharpness. Achieving all of these features at the same time requires specific film formulation and processing conditions especially color development. Not just any conventional color negative film or color developing composition can be used in this manner.
Improved visual contrast may be provided by enhancing film sensitivity in certain regions of the electromagnetic spectrum. For example, U.S. Pat. No. 5,807,666 (Adin et al) describes aerial films that are sensitized in the infrared region to better display tonal separation, provide better haze penetration and improve sensitivity under low visible light conditions.
Specific color negative films designed for aerial photography have been commercialized for many years, for example as KODAK AEROCOLOR Negative Films (Eastman Kodak Company). Such films generally have compositions and structures that are common to multi-color negative films that are processed using conventional Process C-41 processing conditions and chemistry, except that what is known as "color correcting chemistry" is typically omitted from the films. Such chemistry is common for conventional general consumer products where color enhancement and reproduction are essential.
Users of aerial films prefer to obtain images that depict the features on the ground as accurately as possible in what is known as "direct negative interpretation". In addition, the color negative images should be high in contrast and resolution.
Some conventional high-speed color negative films can be used for aerial photography, achieving the desired high contrast and resolution, if they are exposed to lengthy color development. However, there is a need in the photographic industry for a means to achieve high contrast and sharp color images in shorter times without having to make significant and costly changes to processing equipment and chemistry.